1. Field of the Invention
The present invention relates to mechanisms for the formation of the shed in weaving machines. The term "mechanisms" embraces both dobbies of which the weaving program is capable of being easily modified, and simplified mechanisms incorporating cams or the like, which are purely repetitive.
2. History of the Related Art
It is known that, for individually maneuvering the different heddle frames mounted on the loom, such weaving mechanisms comprise an equal number of actuating assemblies (generally called "blades") which are disposed parallel to one another and each of which is formed by a series of rocking members which cooperate with one another to furnish, at the appropriate moment, which is a function of the weave desired for the fabric to be made, the force necessary for the vertical displacement of the corresponding heddle frame. The nature and form of these rocking members vary depending on the different types of mechanisms, however they are most often levers, rods or connecting rods, hooks, roller-holders, etc . . . which have a defined amplitude of pivotal movement. Of course, the identical rocking members of the different actuating assemblies are mounted on a common support shaft mounted in the frame of the weaving machine.
Certain of these rocking members, particularly the retaining hooks and the drawing levers coupled to the heddle frames, are subjected to a high degree of stress so that, to avoid any bending of the common support shafts, it is necessary to employ resistant pieces of large diameter, which because of their size are difficult to install in the frame of the mechanism.
In practice, different modes of mounting the rocking members on the common support shaft have been proposed, of which the three principal ones have been schematically illustrated in FIGS. 1 to 3 of the accompanying drawings.
The most simple assembly is that of FIG. 1, in which the fixed shaft 1 directly supports the rocking members 2 which are disposed side by side without any separation therebetween. Under the conditions, it is clear that these members 2 rub against one another. The frictional forces generated create overheating, substantial wear and defects in the weaving process.
The separated assembly of FIG. 2 was then proposed, in which the members 2, still directly engaged on the common shaft 1, are separated from one another by split rings or circlips 3, retained in grooves 1a machined in the wall of the shaft. In this way, mutual friction of the members 2 is avoided, but the production of the grooves 1a and the assembly of the rings 3 and the members 2 themselves substantially increase the machine cost, at the same time, the grooves 1a considerably weaken the resistance of the shaft 1 to bending.
In order to avoid these drawbacks, the solution illustrated in FIG. 3 has been employed, in which the separation of the rocking members 2 is ensured with the aid of shouldered rings 4 interposed between the support shaft 1 and the hub of each member. Assembly is simplified and the shaft 1 conserves its full resistance, but the rings 4 must be made of special, therefore expensive, metals or alloy in order to resist friction. Furthermore and in particular, area of frictional resistance is increased and, in order to avoid poor performance in the weaving mechanism, the diameter of shaft 1 must be decreased, thus reducing its bending strength.
It is an object of the present invention to overcome these drawbacks, with the aid of a solution which allows the hub of the rocking members to rub directly on a smooth-walled shaft, without any groove, and which nonetheless ensures separation of the members and preventing any mutual lateral friction therebetween.